Signal translator



Patented 8 Sept. 24, l 946 SIGNAL TRANSLATOR Donald D. Grieg, Forest Hills, N. Y., assignor to Federal Telephone and Radio Corporation, Newark, N. J a corporation of Delaware Application May 24, 1943, Serial No. 488,178

9 Claims. 1

This invention relates to radio receivers and particularly to pulse translating means in radio receivers and other electrical apparatus.

It has been proposed heretofore to transmit pulses whose repetition rate or frequency varies according to F. M. (frequency modulation) principle. That is,a train of pulses is modulated as to their repetition rate according to the intelligence to be conveyed thereby.

One of the objects of my present invention is to provide a method and means for translating pulses of varying repetition rate into equivalent time modulated pulses.

Another object of my invention is to provide a radio receiver adapted to detect and translate pulses of varying repetition rate into equivalent time modulated pulses for demodulation in a T. M. (time modulation) demodulator.

According to my invention provision is made for generating locally a train of pulses the time displacement of which is selected according to the repetition modulation characteristics of the pulses to be translated. This local generation of pulses may be performed by any one of several methods whereby the generation may be synchronized' within a given latitude. The repetition modulated pulses are used to resynchronize the local pulse generator upon generation of alternate pulses. That is to say, alternate pulses locally generated are caused to coincide with the occurrence of succeeding pulses of the train of repetition modulated pulses, thereby translating the instant frequency characteristic thereof into a time displacement represented by the intervals between succeeding pairs of pulses. The adjustment of the local pulse generator is such as to provide a normal time displacement between the generated pulses which is less than the minimum repetition interval but greater than one-half the maximum repetition interval of the repetition modulated pulses.

For a further understanding of the invention, reference may be had to the following detailed description to be read in connection with the accompanying drawing, in which:

Fig. 1 is a block diagram of a radio receiver in accordance with my invention; and

Fig. 2 is a graphical illustration showing three separate trains of signal pulses of difierent repetition rates.

Referring to Fig. 1, the radio receiver therein shown is provided with a known detector l having an antenna l2 by which repetition modulated pulses may be detected. It will be understood, of course, that intelligence may be transmitted by repetition modulated pulses by either wire or through space. Also it will be readily apparent that F. M. carrier energy may be transmitted and the intelligence conveyed thereby may be first translated into pulses which vary in repetition rate according to the frequency modulation of, the carrier.

The output of the detector or other source of pulses Of varying repetition rate is applied to a local pulse generator M which preferably is adjustable to produce generated pulses having. a

desired displacement. The generator l4 may be of any known construction in which the operation can be controlled by synchronizing pulses. By way of example, the generator may comprise a form of relaxation oscillator such as a multivibrator having a given mode of operation and which is synchronizable by pulses occurring with in a given latitude of the operating frequency thereof- Such a multivibrator may be arranged whereby the repetition modulated pulses detected control the operation thereof so as to vary the generation for alternate pulses in accordance with the instant repetition rate of the modulated pulses received.

As a further example of a local pulse generator the multivibrator may be associated with a receiver of the triggering oscillator character similarly as'disclosed in the copending application of E. Labin and myself, Serial No. 488,181, filed May 24, 1943. As set forth in more detail in the aforesaid copending application, the triggering oscillator, upon detection of a transmitted pulse, sets 7 up" an oscillation. The establishment of this oscillation, in accordance with the principles of the present invention, triggers the multivibrator or synchronizes the multivibrator in accordance with the reception of the transmitted pulse, thereby initiating a new timing operation for the multivibrator. The output of the multivibrator is applied to the triggering oscillator to increase the sensitivity thereof and consequently vary the blocking potential for the oscillator.

According to the present invention, the local generator 14 is adjusted to repeat its operation before the reception of the next succeeding pulse of the train of repetition modulated pulses. The pulse output of the generator is applied to any suitable T. M. demodulator l6, which for example, may be of the character disclosed in my aforesaid application Serial No. 459,959.

The region of synchronization for the generator precedes the operation thereof a given interval of time during which the generator may be trigg gered from one state of operation to another.

For repetition modulated pulses of a fixed amplitude, this region of synchronization is dependent on the time constants of the pulse generator.

In Fig. 2 there is shown for purposes of illustrating the principles of the invention, a series of curves having the same time base. Curve (2 represents a series of locally generated pulses L having a normal repetition rate T which may be varied within limits of synchronization according to the degree of frequency modulation of the train of pulses to be translated. The intervals of time S preceding each of the pulses L represents the region of synchronization during which the local pulse generator may be triggered by an input pulse. In other words, it is in this region that should a repetition modulated pulse be applied to the generator the generator will be caused to change its timing of the pulse generation. It will be understood, of course, that the pulses L of curve a will shift in occurrence in accordance with resynchronization thereof by an input pulse but that succeeding pulses L will occur thereafter at a time displacement of T until the generator timing is changed by another input pulse.

Curve 1) represents one series of signal pulses B having a repetition rate of T1. The translation of the increment of intelligence represented by this repetition rate is indicated by the pulses of curve 0. The local generator is adjusted so that repetition pulse Bl falls within a synchronizing region S thereby synchronizing the generator for operation to produce pulse BL! in timed relation with pulse Bl. The mode of operation of the generator l4, however, is so chosen that it will produce thereafter at the tim interval T. its next pulse LI before reception of the next signal pulse B2. The displacement between the pulses BL! and LI, therefore, is T according to the mode of operation of the generator. The reception of signal pulse B2 occurs within the synchronizing region SI preceding the next normal operation of the generator which is indicated by broken line 22. It will be noted that the interval between pulse B2 and the broken line 22 is less than the region of synchronization SI of the generator. Therefore, the generator is resynchronized according to the occurrence of the signal B2 to produce pulse BL2 which is displaced from pulse Ll an interval t1 different from interval T.

Following the occurrence of signal E2 the generator operates normally to produce pulse L2. It follows that the next succeeding pulse B3 which falls within synchronizing region S2 will again resynchronize the generator to produce pulse BL3 which is displaced from pulse L2 by the same time interval t1 occurring between pulses LI and BL2. This control of the generator I4 continues for the signal pulses having the repetition rate f1. The increment of intelligence transferred by "the repetition rate ii of the signal pulses B is thus represented by the interval 221 between the pairs of pulses Ll, BL2; L2, BL3; etc.

Curve 11 shows another series of signal pulses D having a repetition rate f2 the occurrence of which is shown as falling Within the region of synchronization S of the generator according to the operating condition of the generator as indicated by curve a. Since curve d represents a change in repetition rate, the first signal pulse DI is shown for purposes of illustration, shifted relative to pulse Bl The region of synchronization S indicated by the line 2!! (curve a) of course, includes the pulse DI since the mode of operation of the generator is so adjusted as to time 4 this region to cover the degree of repetition modulation.

As previously described in connection with pulse Bl the signal pulse DI synchronizes the generator to produce a pulse DLI (curve e). The generator operates normally thereafter to produce impulse L4 displaced an interval .T. from pulses DLI. The signal pulse D2 falling in synchronizing region S3 resynchronizes the generator to produce pulse DL2 displaced from pulse L4 by a time interval 152. This continues for all signal pulses having the repetition rate f2.

Curve g shows still another series of signal pulses G having a repetition rate is. Curve h illustrates the translation of the repetition modulated pulses G into equivalent time modulated pulses in the manner previously described. It will be noted that the interval of time is between pulses L1 and GL2 etc, corresponds to the repetition rate is of the signal pulses G.

Comparing the translation of the signal pulses of the rates f1, f2 and f3 (curves b, d and g) with the time modulated pulses indicated by curves 0, e and h, it will be clear that in accordance with my invention a translation of the intelligence of the repetition modulated pulses into equivalent time modulated pulses is performed. Since I have chosen, for purposes of illustration, increasing repetition rates (that is, decreasing periods) for the signal pulses B, D and G, it will be clear that the time displacement of the corresponding time modulated pulses decreases proportionately as indicated by the time intervals i1, i2 and is.

The T. M. pulses thus produced by the translation of the incoming signal pulses of varying repetition rate are applied to the T. M. demodulator 66. While the demodulator l6 may be of various constructions it preferably is of the character disclosed in my copending application Serial No. 459,959. This demodulation,-for example, preferably is of the character involving the generating or synchronizing of an energy wave having recurring inclined portions, the period of which is comparable to the unmodulated time spacing of the pulses. The wave and the pulses are combined, the pulses being superimposed on the wave at points along the inclined portions thereof according to the time displacement of the pulses. This produces by threshold clipping output pulse energy which varies in amplitude according to the time modulation of the input pulses which may be detected in the usual manner.

While I have shown and described the principles of my invention in connection with specific apparatus, it is to be understood that the description and illustration are given by way of example only and not as limiting the scope of the invention as set forth in the objects and the appended claims.

I claim:

1. A method of translating repetition modulated pulses into equivalent time modulated pulses comprising generating pulsesaccording to a given time displacement and using the successive pulses of a train of repetition modulated pulses to be translated for synchronizing the generation of alternate ones of the generated pulses,

2. The method defined in claim 1 wherein the given time displacement of the generated pulses in absence of said synchronizing operation is selected less than the minimum repetition interval between the repetition modulated pulses.

3. The method defined in claim 1 wherein the given time displacement of the pulses generated in absence of said synchronizing operation is selected less than the minimum repetition interval but greater than one-half the maximum repetition interval of said repetition modulated pulses,

4. A system for translating repetition modu-' lated pulses into equivalent time modulated pulses comprising means to generate pulses at a repetition rate the time displacement of which is less than the minimum repetition interval but greater than one-half the maximum repetition interval of the repetition modulated pulses, means to apply to said generating means for synchronizing control thereof the successive pulses of the train of repetition modulated pulses to be translated, and said pulse generating means being adjustable to a mode of operation such that each of the successive repetition modulated pulses resynchronizes the pulse generating means. 5. The system defined in claim. 4 wherein the generating means is adjustable to produce the pulses at a repetition rate having the desired relation according to the limits of the modulation of said repetition, modulated pulses.

6. A radio receiver having 'means to detect repetition modulated pulses, means to translate the repetition modulated pulses-into equivalent time modulated pulses with alternat pulses equally spaced apart in time relation, the pulses 6 adjacent said alternate pulses being displaced therefrom according to the modulation of the corresponding repetition modulated pulses, and means for demodulating the time modulated pulses.

'7. A radio receiver having means to: detect repetition modulated pulses, means to translate the repetition modulated pulses into equivalent time modulated pulses, the last named means including means to generate pulses having a given time displacement, means for synchronizing the generation of alternate pulses in time relation with successive modulated pulses, and means for demodulating the time modulated pulses.

8. In a pulse system, a source of pulses, a pulse generator for producing discrete pulses at a given repetition rate which is higher than the average pulse repetition rate of said source, and means to apply the pulses of said source to said generator to control the production of alternate ones of said discrete pulses.

9. A pulse system according to claim 8, wherein the pulses of said source vary in repetition rate between two given limits according to signal modulation thereof, the resulting spaces between successive discrete pulses produced by said generator corresponding substantially to the instantaneous repetition rate of the pulses of said source.

DONALD D. GRIEG. 

